Influence of growth ring angle,adhesive system and viscosity on the shear strength of adhesive bonds

Abstract

To investigate the influence of growth ring angle, adhesive system and viscosity on the bonding properties of adhesive bonds, shear tension tests according to DIN EN 302-1 (2004) were conducted using one-component moisture-curing polyurethane, polyvinylacetate and urea-formaldehyde. Significant differences between the systems could be detected, which were reflected in the predominant failure behaviour for each system. Specimens showing wood failure were influenced mainly by the wood factors, whereas samples which had failed in the adhesive part of the bond differed only in the adhesive properties. The growth ring angle showed the same tendencies as it does in plain wood. Therefore, to gain more information on the adhesive performance in the bond, a loading along the LT plane seems more appropriate for beech wood used in DIN EN 302-1 (2004).     

Failure criterion for timber beams loaded in bending,compression and shear

Abstract

Based on the elastic–plastic strength calculation, necessary for precise data explanation, a derivation is given of the failure criterion for combined bending, compression and shear. This exact limit state criterion should replace the unacceptable unsafe criteria of Eurocode 5 (EN 1995-1-1:2004). It is shown that the principle used thus far, of limited “flow” in axial compression as a determining failure criterion, for example, predicting no influence of a size effect, does not hold. Instead, it is derived and confirmed by the data that bending tension failure is always determining, showing the existence of a size effect, and correction of the existing calculation method is therefore necessary. Because of the primary importance of the size effect for the strengths, also for combined bending–compression, a simple derivation of the size effect design equations is given and discussed in an appendix.     

砂土抗剪强度数值模拟的关键技术研究

利用二维颗粒流软件PFC 2D对砂土的抗剪强度进行研究。通过建立数值试样模型、设立相对合理参数、引用＂橡皮膜＂程序等方法对砂土的三轴剪切试验进行数值模拟,模拟的结果较好地反映了砂土的力学性质。     

软弱层带抗剪强度经验公式

软弱层带是控制岩体稳定性的重要边界条件。软弱层带的工程特性是其物质基础与环境条件共同作用的结果。研究表明软弱层带的抗剪强度与塑性、干密度和含水量具有明显的相关性，并提出了抗剪强度与三因子之间的经验公式。     

管壁剪切应力对蜡沉积的影响

根据Fick扩散方程，提出了管流条件下扩散至管壁处可析出蜡分子的沉积系数，用该系数描述了管流中油流的冲刷作用对蜡沉积的影响，通过对新疆的几种油样进行试验研究，结果表明，当温度或流速发生变化从而引起管壁剪切应力变化时，沉积系数随着管壁剪切庆力的增大而减小。     

钢筋混凝土约束梁斜向贴CFRP抗剪加固研究

通过对 1 2根承受集中荷载作用下破坏后补好的矩形截面钢筋混凝土约束梁斜向贴 CFRP抗剪加固试验结果的分析 ,提出了 CFRP有效应变的概念 ,得出了随角度变化 CFRP抗剪承载力计算公式     

框剪结构中剪力墙的设计

探讨了在框剪结构中剪力墙的厚度、数量及长度的确定,从剪力墙的平面、竖向布置方面,阐述了剪力墙的布置。     

Experimental Study on Shear Strength of High Strength Concrete Columns

On basis of the experiment on sixteen high strength concrete columns, their shear behaviors are analysed. The effects of shear-span ratio and axial compression ratio on failure behavior, cracking shear and shear strength are analysed. The authors have discussed the suitability of the design equations for shear strength in the code. This experimental study on shear strength of high strength concrete frame columns is the first one in this field at home and the results can be served as reference for the code of high strength concrete design.     

Modeling of Punching Failure Initiated by Concrete Splitting at Longitudinal Bar Level for Slabs without shear reinforcement

A new punching failure model has been developed for thinner slabs (≤120 mm thick) yet with a larger reinforcement ratio (＞085). On the assumption that the trigger of ultimate failure is the loss of dowel action caused by concrete splitting along the horizontal surface at longitudinal bar level, an equilibrium equation was established and an upper bound solution was obtained. The computation of punching shear capacity shows that for a total of 194 specimens collected, the mean and the coefficient of variation are 1072 and 0.250 respectively. As for the 116 members (out of all 194 ones) with the above character, it is found that there is little change of the mean (equal to 1017) yet an apparent decrease in the coefficient of variation (equal to 0184), which justifies the proposed hypothesis and refined mode in estimating punching resistance of such members.